Back, neck pain sufferers could find relief with spinal disc implants

Every
year, millions of people see doctors for lower back and neck pain.
Cornell engineers in Ithaca and doctors at Weill Cornell Medical College
have created a biologically based spinal implant that could someday
mean relief for countless sufferers.

Larry
Bonassar, associate professor of biomedical engineering and mechanical
engineering, and Roger Härtl, associate professor of neurosurgery at
Weill Cornell Medical College and chief of spinal surgery at
NewYork-Presbyterian Hospital/Weill Cornell Medical Center, have created
an artificial implant to replace intervertebral discs in the spinal
column. Their work is published online July 28 in Proceedings of the
National Academy of Sciences.

In
the body, the discs lie between adjacent vertebrae in the spine and
form a cartilaginous joint to allow movement. The discs can degenerate
or become injured, leading to severe back and neck pain due to vertebrae
rubbing together, or they can herniate and cause compression of nerves
or the spinal cord.

The
scientists began collaborating on the project in 2006, first funded by
an Ithaca-Weill seed grant. Since then, the project has moved into
animal testing stages and has received several awards and accolades, a
$325,000 grant from Switzerland's AOSpine foundation and $100,000 in
support from NFL Charities.

Human
discs look something like a tire, with the outer part, called the
annulus, made of a stiff material, and the inner circle, the nucleus,
made of a gel-like substance that gets pressurized and bears weight.

Bonassar's
lab, which focuses on the regeneration and analysis of musculoskeletal
tissue, engineered artificial discs out of two polymers?collagen, which
wraps around the outside, and a hydrogel called alginate in the middle.
They seeded the implants with cells that repopulate the structures with
new tissue. Remarkably, as opposed to artificial implants today that
degrade over time, the scientists are seeing that the implants get
better as they mature in the body, due to the growth of the cells.

The
implants would treat a broad category of illness called degenerative
disc disease?a leading cause of disability worldwide. According to
Härtl, an increasing number of patients need treatment or surgery from
the degeneration of the intervertebral disc. A surgical procedure
approved by the FDA in 2005 involves removing the disc completely and
replacing it with an implant made of a combination of metal and plastic,
with the aim of mimicking the normal movement of the lumbar and spine.

"Bone
or metal or plastic implants are complicated structures that come with a
mechanical risk of the structures moving around, or debris from the
metal or plastic particles accumulating in the body from wear and tear,"
Härtl said. From a biological perspective, Härtl said, the new discs
could create a "huge advantage" over traditional implants because of how
they integrate and mature with the vertebrae. This major surgery, he
said, would be less invasive, safer and come with fewer long-term side
effects.

The
scientists are hoping to move their experiments into larger animals,
possibly working with Cornell's College of Veterinary Medicine, with the
eventual goal of implanting the devices in humans.